But Germany's EU ambassador at a meeting in Brussels on Thursday said he is not willing to give the green light.

An EU official said the Dutch ambassador also placed a "procedural reserve" on the Netherlands' approval, saying he must consult with The Hague before he makes up his mind.

The development comes after Turkey's violent crackdown on street protests over the past two weeks.

But it does not mean that Wednesday's accession talks are definitely cancelled.

The other 25 EU countries and the European Commission are keen to go ahead.

The German government is also divided on the subject.

Chancellor Angela Merkel this week strongly criticised Turkish leader Recep Tayyip Erdogan. But her foreign minister, Guido Westerwelle, on Thursday said the EU should also open a second chapter - on free speech and freedom of assembly - in reaction to events.

The EU ambassadors will meet again on Monday morning in Luxembourg.

If they cannot agree, EU foreign ministers are likely to tackle the issue at the same venue later in the day.

In the meantime, Turkish officials say they are considering a range of options if Germany upholds its veto.